[Issue 922] export keyword causes undefined references on linux

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=922





------- Comment #1 from thomas-dloop at kuehne.cn  2007-04-05 11:38 -------
(In reply to description)
> Let's say you have a C lib that you want to link with your D app.  You'd have 
a D 'header' like this:
> 
> // need access to global_var defined in the C lib
> export extern extern (C) {
>     int global_var;
> }
> 
> The export keyword is there to facilitate dynamic linking on Windows. 
> On linux, it causes link failure, both with static and dynamic linking.
> "undefined reference to `_imp__global_var'".  This is not a actual error
> message, since I don't have access to a linux box.  But similar errors have
> been reported by others.

Let's avoid any potential "extern" isssues:
#
# export int global_var;
#
# void main(){ printf("%X\n", global_var);
#

a.d:(.gnu.linkonce.t_Dmain+0x4): undefined reference to
`_imp__D1a10global_vari'

> Supposedly, 'export' is not needed with ELF, as all symbols are visible by 
default.
> So I suppose dmd should ignore export on linux?

DMD doesn't use ELF's visibility features, thus export isn't required under 
Linux.

> The workaround we're using is to have a script remove 'export' from the files
> before compiling on linux.  Pretty ugly.  Littering code with version 
statements,
> or reorganizing it so we can put 'version (Windows) export:' somewhere wasn't
> very attractive either.

Another option would be to use the GDC compiler.

Added to DStress as
http://dstress.kuehne.cn/run/e/export_01_A.d


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